My dad has 2200 hours on the Argus, 4X R3350s. In that time he had to shut one down and these were babied (low altitude, low power settings) compared to airline service. I've got calls out to some others who've flown these engines and even to the chief engineer on the two Martin Mars' up here in BC (still flying them).

I think all fighter engines in WW2 were being pulled at less than 200 hours, air and liquid cooled, assuming it lasted that long with no bullet holes in them. In Canada we had DC-4s called Northstars, these used 1760 hp Merlins in place of the radials. They were flown by the RCAF and TCA (now Air Canada). 35 mph faster than the normal DC-4. They ferried a lot of US and Canadian troops to Korea in the '50s and had excellent reliabilty but were reputed to be deafening to ride in.

BSFC can be measured at any air/fuel ratio but is generally measured on dynos at best power and best economy mixtures depending on application. On auto race engines, we generally see best power BSFC figures in the .52-.56 range. A lower cruise rpms, most stock auto engines available in the last 15 years are in the .43-.48 range WOT.

Yes, the Subaru record was run at WOT, about 6000 rpm for 17 days with 3 cars, around the clock. Much higher stresses than what would be seen in aircraft use. Many Lycos and Contis have a 5 minute max power rating and of course as soon as you start climbing, hp is falling off in atmo engines so you are taxing it even less.

Here is an excerpt from GM Powertrain on what they run their engines through if you doubt the strength of auto engines. WOT test 400 hours at 4400-6500 rpm.

Thermal test: 4000 rpm until coolant reaches 260F. Stop it. Rig drains hot coolant, they pump in 0F coolant and wait for block to reach 0F, start it, immediately got to WOT and 4400 rpm. Run it to 260F (about 11 minutes) do it again-600 to 1600 cycles!

Transmission test: WOT and go through every gear to 6200 rpm. Closed throttle to idle in 1st gear- repeat. This is one cycle. They run up to 60,000 cycles! Very hard on rings and transmissions (usually wears out 4-5 transmissions in this test).

Idle test- 2000 hours at idle to test oil flow. Oil taken to 280F.

If it can take this, running along at 4000 or so in cruise is nothing.

As we all know, plenty of aircraft engines don't make it to overhaul without being opened up, especially ones infrequently flown. Ones frequently flown seem to do much better but there is no magic here.

Interesting
 

Not my Lycoming, but I know what you're talking about. Even the B767 has a MAX power time limit. :D I don't think there's any doubt the modern auto engine have earned respect from a reliability stand point. My Acura/Honda has 225,000 on it. Still there's no question a Lycoming's (with out a t/o limitation) can fly @ 100% all day as long as temps/pressures are green.

which is best?
 

I think this thread could go on for ever and ever. In the end, if you analyse what people expect when they choose a particular path, it's pretty easy to judge aforehand whether they are heading for disappointment or delight.

In my opinion, if you choose an auto engine conversion over a Lyclone, hoping for a huge leap forward in some particular area without any other compromises, you will certainly be disappointed.

If you are doing it to capture some incremental improvements in some areas, whilst knowingly being prepared to compromise in others, you will probably be satisfied - maybe even more than satisfied.

A

Absolutely. I'd agree that even the best auto conversion is unlikely to do anything much better than the current air cooled engines except be smoother, burn less oil and perhaps cost less (if you don't count your development time :eek: ). Performance in the air, probably not much different. For me, it is the tinker, design, fabrication, validation part that is of interest plus having something different from the masses. For others buying FF packages, it is turn the key, fly it, smooth power and possibly the difference aspect again. Hey whatever turns your prop. :)

Anybody have a link to this 6,000rpm, 19 day, 100mph average Subaru race test report?

I'd like to read it only because I know that 100mph in my car is not WOT, and it's far less than 6,000rpm (I do understand these are averages as well, hence my wanting to read the actual report).

Lots of interesting stuff in here - I'm still not convinced, but I'm a newbie so who knows ;)

The link is now dead but the meat of it was Subaru took 3 1989 production Legacy's and under FAI supervision set a record of 100,000 km at nearly 135 mph average speed in 19 days. They only stopped for gas, tires and driver changes. Wide open the whole way. No engine problems and all 3 cars finished.

My uncle and cousin were in Italy on business last year and rented a Ford Focus (2L Zetec engine). On the Autostrada they cruised at between 180 and 200 km./hr- almost WOT. They said they were in the lower 50% as far as speed goes and were passed by hundreds of cars over three days of driving. They race karts but said it was still quite an experience. This is simply common in many European countries and especially Germany. I have several friends that cruise at 200-250+ km./hr. on the Autobahn that either live there or rented Opels, BMWs or Mercedes while on vacation. They didn't report the sides of the road littered with broken cars.

According to Wikipedia:It is also mentioned on main Subaru web site, and the Subaru New Zealand site. I recall reading about it in a car magazine at the time. Given that the average speed includes the time for pit stops, tire changes, etc, the speed on the track must have been over 140 mph, and must have been fairly close to full throttle.

Edit - Found a bit more info. At first it looked strange that the FIA site showed the record as being held by Saab at 132 mph, but then I discovered that the Saab record was in a different class.

Longevity factor....
 

Thanks Kevin. I think the Subaru class record was broken last year by a MB turbo diesel- 100,000 MILES at over 145mph. Can't find that link either now.
The point being in both cases, if these engines were not up to the task to being flogged WOT at high revs, they'd frag well before a week of this abuse.

I don't really beat on my Sube, never over 4600 rpm and only 37 inches for T/O, 25-30 in cruise. Just hums along.